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Chemical Bonding
Fajan's Rule Fajan's Rule states that a smaller cation with high charge density has more polarizing tendency than a larger cation with lesser charge density . Ionic Bond An Ionic Bod is formed due to the complete transfer of electrons between interacting atoms . The ionic bonding can be explained using Born - Haber Cycle . The electronegativity difference between the interacting atoms should be more than 2 . Covalent Bond A Covalent Bond is formed by sharing of electrons between two interacting atoms . Covalent bonding gives rise to hard compounds , having high melting and boiling points . Higher the number of covalent bonds , higher is the hardness of compound . Octet Rule The Octet Rule states that the outermost shell of the interacting atoms should have a completely filled octet after formation of a bond . Bond Parameters '''Bond Length''' Bond Length is the distance between the nuclei of the interacting atoms . The smaller the Bond Length the greater is the Bond Strength . '''Bond Angle''' The Angle subtended by the bonds formed by peripheral atoms at the Central atom is called as Bond Angle . '''Bond Enthalpy''' The Energy needed to make or break a Bond is called as Bond Enthalpy . The Bond Enthalpy determines the Bond strength . '''Bond Order''' The number of bonds between two interacting atoms is called as Bond Order . Resonance The formation of electron cloud density in double and triple bond compounds , due to the delocalization of pi electrons , is called as Resonance . Resonance makes a molecule more stable . Polar Character of Covalent Bond When two atoms of different electronegativities form covalent bond , the more elctronegative atom pulls the electron density slightly towards itself . Thus polarity can be achieved in covalent compounds . The more the electronegativity difference , the more will be its polarity . An ionic Bond has more polarity than covalent bonds . A Polar Covalent Bond is an extreme case of Ionic Bond . Dipole Moment = Q x R (Cm) 1 Debye = 3.33564 x 10-30 Cm Covalent Character of Ionic Bond Valence Bond Theory Hybridization The most important postulate of VBT states that the number of Bonds formed is same as the number of unpaired electrons in the central atom . This is achieved by Hybridization . '''sp3 Valency 4''' '''sp2 Valency 3''' '''sp Valency 2''' '''sp3d Valency 5''' '''sp3d2 Valency 6''' Geometry of Molecules Valence Shell Electron Pair Repulsion Theory The Repulsion order is given by Lone Pair - Lone Pair > Bond - Lone Pair > Bond - Bond This theory is successful in explaining the geometry of Molecules . (linear , trigonal planar , tetrahedral , square planar , square pyramidal , pyramidal , bipyramidal and octahedral structures to be studied [Coming Soon!]) [[Molecular Orbital Theory]][[Category:Chemistry]] Molecular Orbitals are formed by the overlapping of two atomic orbitals of two different atoms . Bonding Molecular Orbitals have lower energy than the individual atomic orbitals , i.e. stable . The opposite is applicable for Anti-bonding Molecular Orbitals . The number of Molecular Orbitals is the same as the number of Atomic Orbitals . For Bonding Molecular Orbitals ; b = A + B For Anti-bonding Molecular Orbitals ; a = A - B 1) For every bonding molecular orbital , there is a corresponding anti-bonding molecular orbital . 2) Anti-Bonding Molecular Orbital will be opposite to Bonding Orbital . 3) Bonding Molecular Orbitals will participate in bonding . 4) Generally Anti-bonding Molecular Orbitals are empty . 5) Bonding and Anti-bonding Molecular orbitals can together hold 2 electrons . Orbital Energy Diagram (Homonuclear Diatomic species ) Hydrogen Bonding Polarity in Molecules Dipole Moment (Qualitative aspects only) Dipole Moment = Q x R (Cm) 1 Debye = 3.33564 x 10-30 Cm